When I teach my "Social Media for Artists"class the first thing I talk about is connection. Connecting with people is at the heart of social media. Whereas traditional media (newspapers, radio, etc.) is a one way street, social media is a two-way street.
Funny thing, it turns out how you connect to people in the world is probably how you connect to people online. So let's review for a moment...
How to Connect to People: 1. Make them laugh. 2. Get to know their interests. 3. Offer something they can’t resist. 4. Be a good listener. 5. Tell stories. 6. Be generous. 7. Pay attention to them. 8. Evoke emotion in them.
How does this relate to a Twitter post or a an Instagram pic? It's all about the intention behind your content. If you're just hammering people with promotional posts, it's a real turn off, but if you use one - or, preferably, many - of the ways above to really connect to people, you are far more likely to build a following.
The key is authenticity.
Be yourself and be real. The rest (sales, promotions, etc.) will follow.